The objective of the present study was to explore the effect of carvedilol treatment on metabolic parameters in patients with metabolic syndrome. A total of 77 patients >= 20 years of age (59 females, 18 mates, mean age, 52.3 +/- 10.3) with stage 1 hypertension who fulfilled at least 3 of the metabolic syndrome criteria proposed by NCEP-ATP III were included in this prospective, randomized, controlled study. Patients were randomly assigned to receive daily treatment with carvedilol (n = 27, 12.5 mg/day orally for the first 2 days and 25 mg/day thereafter), atenolol (n = 26, 50 mg/day orally), or doxazosin (n = 24, 2 mg/day orally) for 90 days. Doses were doubled at the end of the 3rd week in patients whose blood pressure was inadequately controlled and amlodipine 10 mg was added to the treatment if the target blood pressure was still not reached at the end of week 6. The biochemical parameters and insulin sensitivity based on the HOMA-IR model were evaluated at baseline and at the end of treatment. Similar reductions in systolic and diastolic blood pressure were observed in all groups (P > 0.05). A significant decrease in HDL cholesterol levels occurred in the doxazosin and atenolol groups compared to the carvedilol group (percent change: -5.6 +/- 13.5 and -8 +/- 9.8 versus -0.1 +/- 12.2, respectively; P < 0.05) and a significant increase in apolipoprotein A1 level was observed in the carvedilol group compared to the doxazosin and atenolol groups (percent change: +4.3 +/- 9.6 versus -0.5 +/- 10.6 and -2.3 +/- 6.6, respectively; P < 0.05). There were no significant differences among the groups with respect to other parameters. It is concluded antihypertensive treatment with carvedilol in patients with metabolic syndrome effectively reduces blood pressure without adversely affecting metabolic parameters.